User’s Reports: Humalog

See also: Kinetic vs Dynamics and Heat & Humalog

Last summer, a few months after Lauren was diagnosed with diabetes, we took a trip to Europe. Although we tried to keep the Humalog cool, there were a couple of times when it was left in the car or it was allowed to warm up. We had problems with control and suspected the Humalog and the heat. We even went to a pharmacy and explained our situation and asked if there could be a degradation of the Humalog. They told us there should not be a problem….. I am interested now that others are having similar probs.

Since then we have suspected similar problems and routinely change out Humalog if it is exposed to warmth. We store the Humalog in the refrigerator. But carry it with us sometimes. I have worried that the Humalog might “spoil” like milk and actually be detrimental to Lauren.

Diane Massey

I have been using Humalog in my insulin pump since I became a pump user in October 1997. I have noticed upon occasion very high blood sugars especially after having my insulin pump in place 2 or 3 days. Knowing that I bolused correctly for my meals I could not figure out what was happening. I would often end up taking 2x the amount of insulin I normally would need! I would check to make sure that the insulin was not blocked and the infusion was taking place but indeed if I replaced the insulin itself I then saw my blood sugars come down. I am very glad I found your article on the internet about this problem. I kept thinking I had some other major problem going on. I always carry an extra vial of insulin with me in case I have a problem with my pump but now I’m a little afraid to have it out of the refrigerator for very long. What can I do to minimize the chance of my insulin going bad?

Thank you.

You are doing the pump community a disservice by posting misinformation. Lispro is as stable as regular insulin at all temperatures tested, according to the company. You should check your sources before giving out anecdotal information.

(Ed: Sorry, we sat on this concern well over 16 months while anecdotal stories kept accumulating from pumpers and shooters that we believe know what they are doing. Lilly certainly tested Humalog before release, including extensive heat testing. However, no lab testing can replicate the real world where tens of thousands of pumpers use Humalog–generally with great success–in all kinds of conditions.)

A Novo rep told me that the reason people suggest using Novolin BR in pumps along with Lispro is to increase sagging sales of BR. Think about it. Both Lispro and BR are phosphate-buffered, and combining them has no scientific basis for increasing “stability”.

(Ed: The difference between Novolin BR or Velosulin and Humalog is not the buffer, but the primary ingredient in the bottle which is Human Regular or Humalog. These proteins are not structurally similar at all. Also likely to be different are the concentration of phosphate buffering required, as well as the concentration of other ingredients like creosol which is used as a preservative. Lilly and Novo don’t publish their formulas for comparison’s sake, to our awareness. And even Velosulin has occasional stability problems in pumps.)

Satisfied pump user in Oklahoma, and love Lispro. It has made a huge difference.

(Ed: We certainly agree. Most people are very satisfied with Humalog, but we also don’t want to hide what we believe to be an occasional problem that can really ruin your day, especially when you don’t know about it.)

Hi, I travel quite a bit for work, and until recently I didn’t worry about refrigerating my insulin when traveling (or at home, for that matter). Since switching to Humalog about 10 months ago, I have noted several occasions when my blood sugar was unusually high for a period of several days and then went back to normal after switching to a new bottle of Humalog. I believe that this has occurred a couple of times with bottles that were getting low (which I had been using for close to a month – I take about 24 units of Humalog per day), and I distinctly recall one event that happened with a new bottle. Unfortunately, I just threw the bottle away less than a week ago… otherwise I would have checked it for particles/cloudiness as you suggested.

For the past several months, I have paid much closer attention to keeping the bottle cool (during a week-long vacation to Crete, where we stayed in a hotel with no in-room refrigerators or ice, I kept it in a wet sock with the tip of the sock in a glass of water and the rest of the sock exposed to the wind in the shade), and haven’t noticed any more difficulties.

How careful must I be to ensure that the bottles don’t freeze? Does it definitely go bad when it freezes? What is the ideal temperature at which to store it?

Any information would be appreciated.
Bob Anderson

I have recently had several clogged infusion sets using Humalog which I have been using about 6 months. I never had this with the Velosulin I used before. I also notice unexplained highs after 2-3 days on the same set. Is there a possibility that Lilly will come out with a mixture of Humalog and Velosulin for the pump, it sounds like a natural blend. I have heard of some who do it now but that only complicates the hard process of priming the set before use. A one product blend would be widely accepted.

John Shuler

I read the report at Humalog and Heat and 72 hours sounds about right. The problem is I only use on average below 50 units of insulin a day. The low use of insulin is due to physical activity, which also contributes to heat degradation since the activity is done outside in hot Texas summers. I do note the problem after about 4 days instead of 3.

Edward G. Schaub
Computational Mechanics Corporation, Inc.
Austin, TX. 78757

I’m on three Humalog injections a day plus NPH in the evening. A vial normally lasts around 20 days. I have noticed periods of time when the Humalog seems to stop working, requiring an increase in the amount I normally take. And yes, this generally occurs near the end of the bottle and a new bottle takes care of it. Your article really caught my eye.

I keep my insulin in an insulated carrier, although I threw out the cold gel pack (they smell after a while). The insulin is at room temperature during use, which is quite a bit longer than the 72 hours your article mentioned. Unused vials remain in the fridge until I need them.

I’m considering switching to a pump. Maybe I’ll go back to Regular, it was always very robust. Unexplained and random variations in blood control are unacceptable.

William McColl <>

When I started pumping, I started with Humalog. Having heard the reports of potential degradation due to heat, I was somewhat over-aware of this situation. Currently, I average between 40 and 45 units per day, split 22.5 in basal, the remainder in bolus insulin. This makes my 315 unit cartridge last about 1 week. I use a Disetronic HTron Plus. The “initial period” of settling into my basals and bolus ratios led to several unexplained high blood sugars.

For a time, I thought that these were more frequent near the end of a cartridge. I started half-filling the cartridges and found that it did not change the incidence of unexplained highs. After working with this for a couple of months, I went back to full cartridges. Eventually, the unexpected highs became less frequent and not associated with any portion of the cartridge. Reflecting on a couple of years experience, I feel that the more common cause of unexplained highs is the degradation of the site by the Humalog (although this itself is not the only cause for these situations). I change sites about every 4 days, but it could vary from 2 to 5 days.

Earlier Bill Van Anterp (I think that I’ve miss-remembered his last name) from MiniMed was asking for anyone who experienced highs that they thought were due to Humalog degradation to send him the tubing and he would test the potency of the insulin. I had planned to send him some of my tubings, but about that time, I was coming to my conclusion that the time that the Humalog had spent in the cartridge didn’t influence my blood sugars. Have you spoken with him to see whether he has any data, rather than anecdotal reports on this phenomena?

I guess that this does not support your contention that Humalog is comparatively unstable to heat. I would be very interested in hearing any other reports that come to you, particularly if they include some measurements.

Jay Watson
home email:

My trial (one week at the beach in the heat) is not directly related to the Humalog stability problem. I was addressing what I see as a much more difficult problem, with many more individual variables. I take care of the insulin I buy, keeping it cold except when I fill the syringe. It seems that the stability problem is much simpler and can be addressed with more controlled studies (something Lilly should do– it wouldn’t take them more than a few weeks and they would know). Just take two fresh bottles of H and R, two not so fresh ones, and two old ones, and leave them at different temps for varying periods of time. Then measure the potency. Very scientific and very straightforward. Of course, there may be individual variables where the insulin temp varies over the course of the day (like sleeping on the pump and keeping it over 90 degrees all night), but at least we would know how the stability compares with R. But knowing how pharmaceutical companies operate, I don’t think they will do this simple evaluation. It is even easier just to make up some regulations based on insufficient and anecdotal data that satisfy their lawyers. Sigh. If I had some ready way to measure the potency I’d do the study myself.


I thought I should tell you that I have been using Humalog in an insulin pen for several months now. I do not keep it refrigerated, but I have never had any problems with it – it’s always been effective (change cartridges about once a month).

Eric Bassin

Since starting on Humalog 6 mos. ago. I too have experienced abnormal highs and pain at the site when the reservoir is about to run out. I never experienced any of this with Velosulin. One day it threw me into ketos. Hot day no air conditioning!! Should I stop using it?


Concerned Diabetic

I recently took a bottle of Humalog all day with me on a trip to New York, I live in Connecticut,…it was unrefrigerated for about 10-12 hours and my blood sugar is lower than ever! there are no particles in the bottle either…


I recently switched to Humalog insulin from Velosulin and have twice (in the past month) encountered problems where blood sugars have been unusually higher (upper 100’s) in combination with ‘NO DELIVER’ alarms from my Minimed 506 pump.

Although hard to correlate to other variables the problem does seem related to exposure to summer heat as in both cases I experienced this condition after outdoor swimming (detach/re-attach from pump using Minimed QR set). And I did use insulin from the SAME bottle of Humalog in both cases when changing my set and did not experience the problem again with subsequent set change.

I do not typically refrigerate the ‘in use’ bottle of insulin and this certainty would become a major and dangerous inconvenience so far as keeping insulin and pump supplies handy at all times should a set change be required.

I do now change my pump infusion set more often than I did before (every 72 hours) which seems to help. But I could go as long as a week or more without a set change with Velosulin and NEVER experience any delivery alarms with Velosulin insulin.

Are there any considerations I should be aware of so far as mixing Humalog with Velosulin? This sort of defeats one of the major advantages of insulin pump usage (ie, using ONE and only ONE insulin preparation!!!).

Thanks for the information on your web site. I have reported this problem to Debbie Moore at the Diabetes Treatment Center in Raleigh, NC.

Steve Koretsky